2019/04/15 by Amir Siraj, Abraham Loeb, Siraj, Amir +1 · 2 citations
Earth and Planetary Sciences · Physics and Astronomy · #Astro and Planetary Science #Atmospheric Ozone and Climate #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Gamma-ray bursts and supernovae
paper · pdf · doi:10.48550/arxiv.1904.07224
openalex publication_date 2019/04/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The earliest confirmed interstellar object, `Oumuamua, was discovered in the Solar System by Pan-STARRS in 2017, allowing for a calibration of the abundance of interstellar objects of its size ∼ 100 m. This was followed by the discovery of Borisov, which allowed for a similar calibration of its size ∼ 0.4 - 1 km. One would expect a much higher abundance of significantly smaller interstellar objects, with some of them colliding with Earth frequently enough to be noticeable. Based on the CNEOS catalog of bolide events, we identify the ∼ 0.45m meteor detected at 2014-01-08 17:05:34 UTC as originating from an unbound hyperbolic orbit with 99.999% confidence. The U.S. Department of Defense has since verified that "the velocity estimate reported to NASA is sufficiently accurate to indicate an interstellar trajectory." We infer that the meteor had an asymptotic speed of v∞ ∼ 42.1 ± 5.5 \mathrmkm s-1 outside of the solar system. Its origin is approximately towards R.A. 49.4 ± 4.1∘ and declination 11.2 ± 1.8∘, implying that its initial velocity vector was 58±6 \mathrmkm s-1 away from the velocity of the Local Standard of Rest (LSR). Its high LSR speed implies a possible origin from the deep interior of a planetary system or a star in the thick disk of the Milky Way galaxy. The local number density of its population is 10^6+0.75-1.5 \mathrmAU-3 or 9 × 10^21+0.75-1.5 \mathrmpc-3 (necessitating 0.2 -- 20 Earth masses of material to be ejected per local star). We show that the detections of CNEOS 2014-01-08, `Oumuamua, and Borisov collectively imply that the differential size distribution in good agreement with a collisional distribution, with a power-law slope is q ∼ 3.6 ± 0.5, where the quoted uncertainty corresponds to 2 σ.